This invention relates to a low density, dimensionally-stable, open-cell, extruded propylene polymer foam blown with a blowing agent comprising partly or entirely of one or more organic blowing agents. The foam offers excellent cushioning properties.
Propylene polymer foams are known in the art, and are useful in many applications such as seen in U.S. Pat. Nos. 3,481,455, 3,871,897, 3,932,569, 4,522,955, and 4,832,770. Such foams have been made with a wide variety of organic and inorganic blowing agents.
It would be desirable to have an open-cell, low density propylene polymer foam (96 kilograms per cubic meter or less) for use in cushioning applications. While closed-cell polyolefin foams, most notably ethylene polymer foams, have typically been used in such applications, it would be desirable to use an open-cell foam for environmental reasons. Open-cell foams lose blowing agent much faster than closed-cell foams. Quick release of blowing agent is important when utilizing volatile blowing agents, the release of which is increasingly subject to governmental regulation. Quick release of blowing agent allows the foam manufacturer to recover all or a substantial portion of the blowing agent prior to providing the foam to the consumer.
It would be further desirable to have an open-cell, low density propylene polymer foam that is dimensionally stable. Open-cell polyolefin foams typically are more difficult to expand to low densities than corresponding closed-cell foams because they lose blowing agent more quickly. It would be desirable to have an open-cell, propylene polymer foam that affords quick release of blowing agent while achieving a high expansion.